1. Field of the Invention
Embodiments of the document relate to a liquid crystal display capable of improving the display quality.
2. Discussion of the Related Art
Active matrix type liquid crystal displays display a moving picture using a thin film transistor (TFT) as a switching element. The active matrix type liquid crystal displays have been implemented in televisions as well as display devices in portable devices, such as office equipment and computers, because of the thin profile of an active matrix type liquid crystal displays. Accordingly, cathode ray tubes (CRT) are being rapidly replaced by active matrix type liquid crystal displays.
The liquid crystal display is driven in an inversion manner, in which polarities of neighboring liquid crystal cells are inverted and the polarities of the neighboring liquid crystal cells are inverted every 1 frame period, so as to reduce direct current (DC) offset and to reduce degradation of liquid crystals. If a data voltage with a predetermined polarity is dominantly supplied to the liquid crystal cells for a long time, image sticking may occur. The image sticking generated when the liquid crystal cells are repeatedly charged to the data voltage with the same polarity is called DC image sticking. For example, when the data voltage is supplied to the liquid crystal cells in an interlaced manner, the DC image sticking occurs. In the interlaced manner, the data voltage is supplied to the liquid crystal cells of odd-numbered horizontal lines during odd-numbered frame periods, and the data voltage is supplied to the liquid crystal cells of even-numbered horizontal lines during even-numbered frame periods. As another example of the DC image sticking, if the same image is moved or scrolled at a certain speed, voltages of the same polarity are repeatedly accumulated on the liquid crystal cells depending on a relationship between the size of a scrolled picture and a scrolling speed (moving speed). Hence, the DC image sticking may appear. Examples of polarity control method for reducing the DC image sticking and the flicker are disclosed in detail in Korean Patent Application Nos. 10-2007-035126 (2007 Apr. 10), 10-2007-0004251 (2007 Jan. 15), 10-2007-0004246 (2007 Jan. 15), 10-2007-0008895 (2007 Jan. 29), 10-2007-0037936 (2007 Apr. 18), 10-2007-0047787 (2007 May 16), 10-2007-0053959 (2007 Jun. 1), 10-2007-0052679(2007 May 30), 10-2007-0062238 (2007 Jun. 25), and 10-2006-0064561 (2007 Jun. 28) and U.S. patent application Ser. Nos. 12/003,585 (2007 Dec. 28), 12/003,666 (2007 Dec. 28), and 12/003,746 (2007 Dec. 31) corresponding to the present applicant, and which are hereby incorporated by reference in their entirety.
A panel (hereinafter referred to as a double rate driving (DRD) panel), in which the number of data lines and the number of output channels of a data drive circuit are reduced by connecting adjacent TFTs on the same display line to the same data line, has been developed so as to reduce the circuit cost of the liquid crystal display. According to an experimental result obtained by applying the above-described polarity control method to the liquid crystal display including the DRD panel, 30 Hz-flicker, a flicker in a line direction, a flicker in a column direction, a color distortion in which one of red, green, and blue is remarkably showed, and the like, appeared. Accordingly, technology capable of reducing the DC image sticking, the flicker, the color distortion, etc. has been required even in the liquid crystal display including the DRD panel.